1. Field of the Invention
The invention relates to a sewing machine having a threading device for threading an eyelet of a looper, and more particularly to a sewing machine having a threading device designed to effect threading by advancing a thread pusher together with a thread into the eyelet of the looper and then retracting the thread pusher only from the eyelet of the looper.
2. Description of Related Art
In a chain stitch sewing machine, a lower looper is provided so as to be swingable in synchronism with a needle bar. In a conventional chain stitch sewing machine, an operation of threading an eyelet of the lower looper is manually carried out by an operator with use of a pincette.
However, in the conventional chain stitch sewing machine, other parts are arranged around the periphery of the lower looper, so that the threading operation using a pincette is complicated and requires considerable skill. In this circumstance, an operator of little skill is apt to make an error in the threading operation. In particular, since the thread to be inserted through the eyelet of the lower looper is usually a special thread, such as a thick thread or a stretchable thread, the threading operation is difficult for the operator.
As a technique to cope with this problem, there is disclosed a threading device in Japanese Patent Publication No. 61-18473. This threading device includes a complicated link mechanism and it is, therefore, very difficult to install the device in the bed of a sewing machine body. Moreover, manufacturing costs are increased and it is also very difficult to manufacture a sewing machine having such a threading device.